Today there are numerous types of devices for flow control, such as for controlling oil and gas flow to specific flow rates. One valve type used for this purpose is needle valves. Needle valves are a valve type having a small flow orifice and a needle shaped stem allowing for an accurate flow control at relatively low flow rates. Other ranges of use are steam injectors and fuel injectors in combustion engines and gas turbines.
In a needle valve, a needle-shaped spindle is arranged, having a stroke direction axially in a flow channel, and is movable in relation to a conical seat. The outlet of the valve does typically exhibit a uniform flow cross section. A problem that arises in valves of this type, is erosion caused by particles and droplets hitting the seat surface at the inlet section. Another problem is erosion in the conical surface of the seat at the low-pressure side of the valve, because of turbulent flow. Moreover, these mechanical forces acting upon the valve may cause vibration in a valve and accompanying fittings, which in turn may shorten the lifetime of the fittings.
For applications in oil and gas installations offshore, where valves constitute a part of subsea structures, a valve breakdown is naturally very unfortunate, since a production shutdown itself is expensive. Moreover, exchange of valves in environments like this is time and cost consuming.